The following description relates to a relay, and more particularly to a relay capable of causing a movable contact point to accurately and stably contact a stationary contact point for conduction even after an arc is generated.
A relay is an electromagnetic switching apparatus for an electric relaying operation, and generally defines a connection switching apparatus capable of conducting or interrupting a main circuit in response to a small input current change. Various types of relays are available including a contact relay, a non-contact relay, a pressure relay and an optical relay but the contact relay is mostly used for automobile indicator lights and wiper motors of an automobile as the contact relay has a relatively simple structure.
FIG. 1 illustrates an exemplary contact relay, and as shown in FIG. 1, the contact relay includes an electric magnet 1, a movable rod 2 movably sucked by operation of the electric magnet 1, a movable contact point 3 disposed at a distal end of the movable rod 2, upper/lower stationary contact points 4, 5 for opening and closing a circuit by being contacted to the movable contact point 3, and restoring lever 6 coupled at the other end of the movable rod 2 and resiliently moving in an opposite direction from the movably sucked movable rod 2. The conventional relay thus configured is operated in the following manner.
That is, when a current is introduced into the electric magnet 1, the electric magnet 1 sucks the movable rod 2 to cause the movable contact point 3 disposed at the distal end of the movable rod 2 to be brought into contact with the lower stationary contact point 5. The contact between the movable contact point 3 and the lower stationary contact point 5 causes the current to flow from a movable terminal (not shown) connected to the movable rod 2 to a stationary terminal (not shown) connected to the lower stationary contact point 5, whereby a main circuit connected to a relay is conducted.
However, when there is a need to interrupt the main circuit for protecting or controlling the main circuit against damage by an over-current, the current is no more introduced into the electric magnet 1. When the current is not introduced into the electric magnet 1 any more, the electric magnet 1 can no more pull the movable rod 2, and the movable contact point 3 mounted on one end of the movable rod 2 is disengaged from the lower stationary contact point 5 by the restoring lever 6.
When the movable contact point 3 is disengaged from the lower stationary contact point 5 to disable the movable contact point 3 and the lower stationary contact point 5 to contact each other, the relay is opened to interrupt the main circuit connected to the relay. At this time, the movable contact point 3 comes to contact the upper stationary contact point 4 to cause the current to flow to another point on the main circuit, whereby the main circuit may be controlled.
Meanwhile, the restoring lever 6 may be replaced by an elastic member like a spring, and when the movable contact point 3 is instantly disengaged from the lower stationary contact point 5, an arc may be generated. Furthermore, the relay may be filled therein with an insulating gas such as SF6 in order to distinguish the arc promptly.
However, the thus described conventional relay suffers from a drawback in which the relay is not properly operated if the movable rod 2 develops a problem because the movable contact point 3 and the upper/lower stationary contact points 4, 5 are engaged or disengaged (brought into contact or out of contact) via the movable rod 2.
That is, if a hinged part of the movable rod 2 coupled to the restoring lever 6 is twisted when an arc is generated, there may be generated a problem of the movable contact point 3 not being brought into contact with the upper/lower stationary contact points 4, 5 even if the current is introduced into the electric magnet 1 again.
The conventional relay suffers from another drawback in that the movable rod 2 may not be guidably pulled to or disengaged from the electric magnet 1 to cause the movable contact point 3 disposed at one end of the movable rod 2 to be accurately brought into contact with the upper/lower stationary contact points 4, 5.
These drawbacks may generate resistance at a portion where the movable contact point 3 and the upper/lower stationary contact points 4, 5 are brought into contact, which may further give rise to an unexpected heat to damage the movable contact point 3 and the upper/lower stationary contact points 4, 5.
Furthermore, even if the conventional relay is mounted with a structure that guides the movable rod 2, the structure must be made of an insulating material such as plastic or the like because the structure is not allowed to electrically conduct the movable rod 2. However, the insulating material such as plastic usually lacks a good wear and tear, such that dust may be generated from the structure by contact friction when the movable rod 2 moves. The dust of the structure may stick to the movable contact point 3 or the upper/lower stationary contact points 4, 5 to become an obstacle to the electrical conduction.